To ensure the safety of biopharmaceuticals, regulatory agencies impose stringent purification standards and quality attributes (identity, strength, and purity) for proteins intended for human administration. The standards mandate that protein-based therapeutic products are substantially free from impurities, including product related contaminants, such as aggregates, fragments and variants of a recombinant protein, and process related contaminants, such as leached chromatography resins, media components, DNA, host cell proteins, viral contaminants and endotoxins.
Process development can often be the rate-limiting step in the production of suitable quantities of biopharmaceutical drug candidates for clinical trials. Manufacturers of recombinant biopharmaceuticals have to deliver products with consistent quality attributes in order to assure reproducible clinical performance. Production of high purity biopharmaceuticals to support clinical development usually requires more than a single-step purification process. One of the greatest challenges in the development of a biopharmaceutical is the establishment of efficient and cost effect manufacturing processes which can reproducibly produce product of sufficient purity and biological activity.
Typically, down-stream processing of recombinant proteins relies heavily on process chromatography, with between two and five chromatography unit operations. Because downstream processing constitutes between 50-80% of all manufacturing costs, the biopharmaceutical industry considers bioprocess development as in integral component of product development and as a source of competitive advantage. Accordingly, companies involved in the large-scale manufacturing of monoclonal antibodies (mAbs) have made significant investments to establish upstream and downstream bioprocess platforms, in order to ensure their ability to consistently produce large quantities of pharmaceutical-grade mAbs.
Commercial scale purification processes typically include at least the following steps: cell lysis to recover an intracellular protein or recovery of a protein from the media in case of a secreted protein; removal of cellular debris using differential centrifugation or filtration to obtain a clarified sample containing the protein of interest; use of a variety of chromatography media in a multi-step process to separate a protein of interest from the various impurities in the sample. The primary consideration in downstream process development is drug purity. In addition, the process must be robust, reliable and scalable (Shukla, A et al. Journal of Chromatography B, 848:28 (2007).
Despite the recognized advantages of a having an established purification platform, differences in the biochemical properties and purification behavior of individual mAbs has led to the realization that downstream processing cannot be reduced to a single templated process that will be generally applicable to every biopharmaceutical drug. As a result, downstream purification processes have evolved towards defined operation parameters and a set of unit operations which are employed to create a common framework that is suitable for use the development of a product-specific process. The operation parameters serve to establish performance expectations for the individual unit operations and to bracket acceptable operating conditions, thereby limiting the amount of experimentation required to develop a protein-specific purification scheme. In practice, the unit operations initially developed for the downstream processing of mAbs can be modified for use in the development of processes suitable for use in the manufacturing of alternative types of biopharmaceuticals, including human IgG Fc fusion proteins.
Currently, there is still an unmet need for efficient and robust purification methods for Fc-fusion proteins which are amenable to the large-scale production of final products that are suitable for human administration.
The references cited in the present application are not admitted to be prior art to the claimed invention.